In general, scissors are a device comprising two blades that are connected together such that, when an operator applies manual pressure, the blades slide past each other, producing a shearing action that cuts a material inserted between the blades. The earliest scissors, dating back over 3000 years to ancient Egypt, were of the “spring” design, having two blades connected at the handle by an arcuate strip of metal that keeps the blades apart until manual pressure is applied. The current “cross-bladed” design originated with the Romans about 100 AD. In this form, scissors comprise two blades conjoined at a pivot, with each blade connected via a shank to a ring or loop that accommodates one or more fingers. Mechanically, such scissors constitute a first-class double-lever system, with the pivot acting as the common fulcrum.
Scissors can be configured as either right-handed or left-handed, with one configuration being the mirror-image of the other. When the blades are fully separated, the scissors are said to be in an open position, as opposed to the closed position, in which the blades fully engage each other along their length.
Aside from anatomical variability, the uses to which scissors are put will also influence the optimum ergonomic design. In cutting cloth, for example, the scissors are usually held vertically, with the tip pointing away from the operator. In cutting human hair, on the other hand, the scissors may be held vertically, for trimming the temples, or horizontally, for trimming the top of the head, with the tip generally pointing to the left for a right-handed operator. Pet groomers, however, will also need to hold the scissors vertically, with the tip pointing up or down, in order to trim the flanks and legs of the animal. Since the orientation of the hand on the scissors will be different in each of these applications, no single non-adjustable design will be ergonomically optimal for all of them.
The prior art includes a number of designs that are adjustable with respect to one or more parameters. These parameters include: Thumb offset: the location of the thumb ring with respect to the finger ring; Thumb/finger ring rotation: to control roll, yaw and pitch; and Thumb/finger ring size adjustment.
Several patents provide for a thumb ring that floats along the lower shank of the scissors. The earliest of these dates back to 1923 in the patent of Gosha, U.S. Pat. No. 1,479,908. Later examples are the patents of Dolph, U.S. Pat. No. 2,158,277, disclosing a ratchet clip mount for a finger ring. Chuba, U.S. Pat. No. 2,744,324, discloses a pinch bolt arrangement for securing a thumb ring along the length of the shank, and Pinto, U.S. Pat. No. 4,146,961 discloses a perpendicularly oriented thumb loop adjustably secured to the shank with a fastener.
Pivoting thumb rings of various types are disclosed in the prior art going as far back as 1897, in the Nolen patent, U.S. Pat. No. 590,330. Later examples of pivoting thumb ring designs are the Pracht patent, U.S. Pat. No. 5,109,608 and the Brenton application, US 2005/0204569. In each of these designs, the thumb ring rotates about the vertical axis however, operation of the scissor blades still requires the operator's hand to open and close in a typical fashion which results in fatigue and may result in more serious consequences such as carpal tunnel syndrome.
Gauvrey, U.S. Pat. No. 4,642,895, discloses a thumb ring mounted on a sleeve that slides along the lower shaft of the scissors. The thumb ring includes a ball and socket arrangement that allows the thumb ring to pivot polyaxially with respect to the shank.
Lauritzen et al., Pub. No. US 2006/0064879, teaches a thumb ring that's integrated with a sleeve which slides along a shortened lower shaft and also rotates around the lower shaft. A ball-and-socket joint connecting the finger ring to a curved upper shaft enables rotation of the finger ring. However, like Gauvey, the scissors must still be opened and closed in a conventional manner.
None of these provide for alternative motion to operate the blades of the scissors. Consequently, these designs cannot provide an ergonomic motion for the operator's thumb and ring finger, which will diminish efficiency and comfort of use. Nor do these designs provide any means for rotating the thumb and/or finger rings to achieve optimal control over the roll, yaw and pitch of the scissors. Without such rotation features, all rotational movement must be achieved purely by wrist movements. While the anatomy of the wrist comfortably lends itself to rolling rotation, through a range of about 180 degrees, the same is not true of yaw and pitch, which demand awkward twisting of the wrist through a very constrained range of motion.
Consequently, there remains a need, as yet unmet by the prior art, for ergonomic scissors that eliminate the hand motions required by typical scissor constructions. Finally, there are ergonomic needs that scissors having an alternative operative motion must satisfy in order to achieve acceptance by the end user. The scissors should also be easily and quickly disassembled and reassembled for cleaning and maintenance using minimal hardware and requiring a minimal number of tools. Further, the system should not require excessive strength to assemble or include hard to manipulate component parts. Moreover, the system must assemble together in such a way so as not to detract from the aesthetic appearance of the scissors.
Thus, the present invention provides slide operated scissors which overcome the disadvantages of prior art scissors and shears. The slide operated scissors of the present invention not only provide for alternative operative motion, they also provide relative ease in the disassembly and reassembly for maintenance and cleaning.